In NA44, the trigger-level centrality selection combines T0 multiplicity discrimination with the inherent centrality-biasing effect of the narrow midrapidity acceptance of the spectrometer. This makes the centrality normalization of the particle yields in this experiment particularly difficult. (The nature of the problem will be explained in Subsection 4.2.1.) In the present work, centralities of the physics settings were determined from 1995 data using the Si pad array multiplicity, via a method developed by the author to respond to the specific challenges of this particular experiment and a particular data set. In this method, the trigger centralities play the role of ``calibration constants'' that ensure consistency of the absolutely normalized spectrometer and Si data. Apart from the normalization factors themselves, this section provides justification of the method and gives a reasonable amount of technical background information.
matching: Si vs spectrometer